US4013338A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fourier transform holography using pseudo-random phase shifting of object illuminating beams and apodization
Assignee: Panasonic Holdings Corp
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Filing: 1976-01-26
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Granted: 1977-03-22
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Expires: 1996-01-26
Abstract
Abstract A phase mask comprised of a square array of phase shifting areas arranged in pseudo-random pattern is illuminated with a beam of electromagnetic radiation, as a result of which an array of pseudo-randomly phase shifted beams emerges from the phase mask and impinges upon an object transparency to be intensity-modulated thereby and come to a focus on a Fourier transform plane. The power spectrum of the beams distributes in orthogonal directions on the Fourier transform plane from its center maxima in a distinct pattern of series of fringes. The technique of apodization is employed to suppress the fringes to thereby reduce the coherent noise of a hologram to a minimum.
Inventors
- 👤 Isao Sato
- 👤 Makoto Kato
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 23:23
CPC Classifications
G; G03; G03H; G03H1/00; G03H1/04; G03H1/16; G03H1/0402; G03H1/041; G03H2223/00; G03H2223/13; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
161 words
A system for forming a hologram of an array of beams of electromagnetic radiation on a Fourier transform plane, comprising: a pseudo-random phase mask receptive in use of a beam of electromagnetic radiation and comprised of a plurality of phase shifting areas arranged in a pattern of rows and columns, there being an approximately equal number of phase shifting areas for each of the different phase shifts, wherein the number of different phase shifts is N which is greater than three inclusive and each of the different phase shifts is one of the multiples of m360°/N, where m ranges from 1 to N, and the phase difference between orthogonally adjacent phase shifting areas is 360°/N, whereby the power spectrum of each of said phase-shifted beams on the Fourier transform plane distributes in orthogonal directions from the center maximum of the power spectrum; means for apodizing the phase-shifted beams; and means for recording a Fourier transform hologram of said phase-shifted, apodized beams.
Claim 2
Independent Claim
161 words
A system for forming a hologram of an array of beams of electromagnetic radiation on a Fourier transform plane, comprising: a pseudo-random phase mask receptive in use of a beam of electromagnetic radiation and comprised of a plurality of phase shifting areas arranged in a pattern of rows and columns, there being an approximately equal number of phase shifting areas for each of the different phase shifts, wherein the number of different phase shifts is N which is greater than three inclusive and each of the different phase shifts is one of the multiples of m360°/N, where m ranges from 1 to N, and the phase difference between orthogonally adjacent phase shifting areas is 360°/N, whereby the power spectrum of each of said phase-shifted beams on the Fourier transform plane distributes in orthogonal directions from the center maximum of the power spectrum; means for apodizing the phase-shifted beams; and means for recording a Fourier transform hologram of said phase-shifted, apodized beams.
Claim 3
Dependent Claim
55 words
A system as claimed in claim 1, wherein said apodizing means comprises an aperture mask comprised of an array of apertures having one-to-one correspondence with the phase shifting areas of said phase mask, each of said apertures having a substantially Gaussian light transmission characteristic to impart a Gaussian intensity distribution to a beam passing therethrough.
Claim 4
Dependent Claim
70 words
A system as claimed in claim 2, wherein each of said apertures is square shaped and wherein the length of the edges thereof is equal to 2λf/D H , wherein λ is the wavelength of the beam, f is the focal length of a Fourier transform lens disposed between the pseudo-random phase mask and the recording means, and D H is the length of edges of said Fourier transform hologram.
Claim 5
Dependent Claim
21 words
A system as claimed in claim 1, wherein said apodizing means is a filter disposed in front of said recording means.
Claim 6
Dependent Claim
58 words
A system as claimed in claim 1, wherein each of said phase shifting areas has a phase difference of 90° with respect to orthogonally adjacent areas and phase differences of one of 0° and 180 ° with respect to orthogonally adjacent areas which adjoin the first mentioned orthogonally adjacent areas remote from said each of phase shifting areas.
Claim 7
Independent Claim
202 words
A method for reconstructing a Fourier transform hologram, wherein said hologram is prepared by a method comprising the steps of directing a beam of electromagnetic radiation to a pseudo-random phase mask comprised of a plurality of phase shifting areas arranged in a pattern of rows and columns, there being an approximately different phase shifts, wherein the number of different phase shifts is N which is greater than three inclusive and each of the different phase shifts is one of the multiples of m360°/N, where m ranges from 1 to N, and the phase difference between orthogonally adjacent phase shifting areas is 360°/N, to produce a plurality of phase-shifted beams, placing an object transparency behind the phase mask in the direction of the beam to intensity-modulate the phase-shifted beams, subjecting a recording medium to the intensity-modulated, phase-shifted beams and directing a reference beam to said recording medium to produce an interference fringe pattern with said intensity-modulated, phase-shifted beams, said method comprising: directing a beam of electromagnetic radiation to said hologram, said beam having a uniform intensity distribution across the transverse cross-section thereof; and placing an apodization filter in the path of said beam to impart a substantially Gaussian intensity distribution to said beam.
Claim 8
Independent Claim
202 words
A method for reconstructing a Fourier transform hologram, wherein said hologram is prepared by a method comprising the steps of directing a beam of electromagnetic radiation to a pseudo-random phase mask comprised of a plurality of phase shifting areas arranged in a pattern of rows and columns, there being an approximately different phase shifts, wherein the number of different phase shifts is N which is greater than three inclusive and each of the different phase shifts is one of the multiples of m360°/N, where m ranges from 1 to N, and the phase difference between orthogonally adjacent phase shifting areas is 360°/N, to produce a plurality of phase-shifted beams, placing an object transparency behind the phase mask in the direction of the beam to intensity-modulate the phase-shifted beams, subjecting a recording medium to the intensity-modulated, phase-shifted beams and directing a reference beam to said recording medium to produce an interference fringe pattern with said intensity-modulated, phase-shifted beams, said method comprising: directing a beam of electromagnetic radiation to said hologram, said beam having a uniform intensity distribution across the transverse cross-section thereof; and placing an apodization filter in the path of said beam to impart a substantially Gaussian intensity distribution to said beam.
Claim 9
Independent Claim
192 words
A method for reconstructing a Fourier transform hologram, wherein said hologram is prepared by a method comprising the steps of directing a beam of electromagnetic radiation to a pseudo-random phase mask comprised of a plurality of phase shifting areas arranged in a pattern of rows and columns, there being an approximately equal number of phase shifting areas for each of the different phase shifts, wherein the number of different phase shifts is N which is greater than three inclusive and each of the different phase shifts is one of the multiples of m360°/N, where m ranges from 1 to N, and the phase difference between orthogonally adjacent phase shifting areas is 360°/N, to produce a plurality of phase-shifted beams, placing an object transparency behind the phase mask in the direction of the beam to intensity-modulate the phase-shifted beams, subjecting a recording medium to the intensity-modulated, phase-shifted beams and directing a reference beam to said recording medium to produce an interference fringe pattern with said intensity-modulated, phase-shifted beams, said method comprising, directing a beam of electromagnetic radiation to said hologram, said beam having a substantially Gaussian intensity distribution across the transverse cross-section thereof.
Claim 10
Independent Claim
192 words
A method for reconstructing a Fourier transform hologram, wherein said hologram is prepared by a method comprising the steps of directing a beam of electromagnetic radiation to a pseudo-random phase mask comprised of a plurality of phase shifting areas arranged in a pattern of rows and columns, there being an approximately equal number of phase shifting areas for each of the different phase shifts, wherein the number of different phase shifts is N which is greater than three inclusive and each of the different phase shifts is one of the multiples of m360°/N, where m ranges from 1 to N, and the phase difference between orthogonally adjacent phase shifting areas is 360°/N, to produce a plurality of phase-shifted beams, placing an object transparency behind the phase mask in the direction of the beam to intensity-modulate the phase-shifted beams, subjecting a recording medium to the intensity-modulated, phase-shifted beams and directing a reference beam to said recording medium to produce an interference fringe pattern with said intensity-modulated, phase-shifted beams, said method comprising, directing a beam of electromagnetic radiation to said hologram, said beam having a substantially Gaussian intensity distribution across the transverse cross-section thereof.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-03-21 | 1980-09-20 | 1981-03-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-21 | 1984-09-20 | 1985-03-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-21 | 1988-09-20 | 1989-03-22 | $7700.00 | Window Closed / Lapsed |